A driveline of a hybrid vehicle may include a driveline disconnect clutch. The driveline disconnect clutch may be positioned in the driveline between an engine and an integrated starter/generator. The driveline disconnect clutch may be closed when driver demand torque request levels are high or when an electric energy storage device is being charged. The driveline disconnect clutch may be open when driver demand torque request levels are low and when an integrated starter/generator solely propels the hybrid vehicle. The driveline disconnect clutch may be hydraulically applied and released, and a transmission pump may supply pressure to apply the driveline disconnect clutch. However, operating the transmission pump to maintain the driveline disconnect clutch in a closed state may increase energy used to operate the driveline. Therefore, it may be desirable to develop a way of operating the driveline disconnect clutch in a way that may improve driveline efficiency.
The inventors herein have recognized the above-mentioned issues and have developed a driveline operating method, comprising: receiving a driver demand torque to a controller; and adjusting a torque capacity of a driveline disconnect clutch via the controller responsive to the driver demand torque and an offset torque.
By adjusting a torque capacity of a driveline disconnect clutch responsive to driver demand torque, it may be possible to improve driveline efficiency while providing expected driveline disconnect clutch operation. In particular, transmission line pressure (e.g., hydraulic pressure output of a transmission pump, which may be regulated via a pressure regulator or via adjusting transmission pump efficiency) may be adjusted to provide a driveline disconnect clutch torque capacity that is a function of driver demand torque and a torque offset. In one example, the disconnect clutch torque capacity is a greater of a requested engine torque and an actual engine torque plus an offset torque, and the requested engine torque is a driver demand torque minus an energy management torque. In this way, transmission line pressure may be controlled to close the driveline disconnect clutch and maintain the driveline disconnect clutch closed without slipping while not having to operate with transmission line pressure at a maximum value. In other words, the transmission line pressure may be adjusted to hold the driveline disconnect clutch closed with little additional force to keep the driveline disconnect clutch closed.
The present description may provide several advantages. Specifically, the approach may provide increased driveline efficiency. Further, the approach may extend the duration of a driveline component's life cycle. Additionally, the approach hold the driveline disconnect clutch closed during static and dynamic driver demand torque conditions.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.